There are already known various constructions of compressors, among them so-called scroll or scroll-type vapor compressors which are becoming increasingly popular particularly for air conditioning applications, especially in the one-to-ten ton cooling capacity range. Among the characteristics that make such scroll compressors more attractive for many applications than reciprocating compressors are their high efficiency, reduced number of moving parts, low noise, and low vibration. An example of a scroll compressor of the type here under consideration is disclosed in the U.S. Pat. No. 4,715,796, for instance.
Major components of a typical scroll-type vapor compressor include a support usually constructed as a housing for some or all of the other major components, fixed and orbiting scroll elements, a drive shaft provided with an eccentric crank portion and mounted on the support for rotation by respective support bearings, and a drive motor which rotates the drive shaft about its axis so that the crank portion causes the orbiting scroll element to conduct orbiting motion relative to the fixed scroll element, with the orbiting element being prevented by an appropriate coupling arrangement of any known construction from rotating with the drive shaft while still being capable of conducting the desired orbiting movement. Vapor compression is achieved in at least one compression space bounded by the fixed and orbiting scroll elements as the orbiting scroll element is driven by the eccentric crank shaft portion, and the pressure of the medium being compressed acts on both the fixed scroll element and the orbiting scroll element. As a result of the rotational and particularly the eccentric and orbiting motions of the various components, and also of the forces attending the compression process, loads are transmitted to the drive shaft and reacted by the support bearings.
In an attempt to reduce the vibration and bearing loads, it has been already proposed to mount respective counterweights on the drive shaft for joint rotation with the drive shaft. In the heretofore proposed scroll-type compressor constructions in which the axis of the drive shaft may typically be oriented vertically and the scroll elements may be situated on top during the operation, the upper counterweight as considered in this mounting position is positioned close to the crank portion in the axial direction and 180 degrees from the crank portion in the circumferential direction, while the lower counterweight is much smaller than the upper counterweight and is circumferentially aligned with the crank portion.
Thus, the balancing of existing scroll compressors appears to follow the practice used with reciprocating compressors wherein only inertial forces are typically considered in sizing and positioning counterweights. While this approach is valid for reciprocating compressors since the pressure component of the resultant force vector acting on the crank fluctuates greatly in magnitude and somewhat in direction relative to the crank, and therefore cannot be dynamically balanced, experience has shown that in scroll compressors this approach results in a much higher degree of loading of the support bearings than necessary.
Accordingly, it is a general object of the present invention to avoid the disadvantages of the prior art.
More particularly, it is an object of the present invention to provide a scroll compressor which does not possess the disadvantages of the known compressors of this kind.
Still another object of the present invention is to develop the scroll compressor of the type here under consideration in such a manner as to reduce the loading of the support bearings of its rotating drive shaft under operating conditions.
It is yet another object of the present invention to design the scroll compressor of the above type in such a manner as to be relatively simple in construction, inexpensive to manufacture, easy to use, and yet reliable in operation.
A concomitant object of the present invention is to devise a method of balancing the compressor of the above type by choosing the sizes and positions of counterweights mounted on the crankshaft in such a manner as to minimize the support bearing loading.